1. Field of the Invention
This invention is broadly concerned with an electrical capacitance instrument and a manufacturing method of the same and intended particularly to be used to improve a high-volume productivity of electrical capacitance instrument and a manufacturing method thereof.
2. Description of the Related Art
Conventionally, in the art of measuring instruments such as slide calipers, there has been employed an electronic one having a digital display to prevent or decrease artificial mistakes when reading out measured value with the eye.
The conventional electronic measuring instrument is generally defined by a main body and a measuring element adapted to move in relation to the main body. The instant displacement value of the measuring element is transformed into electrical signals by conventionally known electrical capacitance instrument to be displayed in numerical values.
The electrical capacitance instrument includes a main scale which has a plurality of electrodes thereon arranged at a fixed spacing from one another and a measuring element which has electrodes corresponding to the electrodes provided on the main scale in a statically relating state. The displacement value of the measuring element is transformed into electrical signals based on the electrical capacitance changed in accordance with the displacement value of the measuring element.
Incidentally, the main scale is generally manufactured separately from a main body of the instrument and then secured on the main body by means of a bonding agent.
However, the manufacturing process for the main scale does not attain a high-volume productivity due to several steps, that is, a step for evaporating metal membrane on a base plate made from epoxy-glass having insulation properties, a step for masking necessary area on the metal membrane, a step for forming plural electrodes by etching unnecessary area on the metal membrane, and a step for forming an insulation membrane to cover surface of the electrodes.
It would be therefore difficult to achieve a preferable high-volume productivity of the measuring instrument having such a main scale even though the production of other parts except the main scale will be improved.
Accordingly, an object of the present invention is to provide an ideal electrical capacitance instrument for high-volume production and a manufacturing method of the same.